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      <title>WebSocket 与 HTTP 的区别 - 交互式测验</title>
      <style>
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            max-width: 900px; /* Wider to accommodate buttons */
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        .quiz-header {
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          color: white;
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          text-align: center;
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        .quiz-header h1 {
          margin: 0;
          font-size: 24px;
          font-weight: 700;
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        .quiz-header p {
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            font-size: 14px;
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        .quiz-body {
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        .progress-bar {
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        .option-item {
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          border: 1px solid #dee2e6;
          border-radius: 8px;
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          margin-bottom: 12px;
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          transition: background-color 0.2s ease, border-color 0.2s ease;
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        .option-item:hover {
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        .option-item.selected {
            background-color: #d1e7fd;
            border-color: #4a90e2;
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        .quiz-footer {
          padding: 20px 30px;
          display: flex;
          justify-content: space-between; /* 将按钮分布在两侧 */
          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
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        #next-btn {
            background-color: #28a745;
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        .nav-btn:hover {
          background-color: #357abd;
          transform: scale(1.05);
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        .nav-btn:disabled {
            background-color: #a0c3e8;
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        .result-box {
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            padding: 20px;
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        .result-box.correct {
            background-color: #d4edda;
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            color: #155724;
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        .result-box.incorrect {
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            color: #721c24;
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        .result-box h3 {
            margin-top: 0;
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        .explanation-text {
            margin-top: 15px;
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        .source-text {
            font-style: italic;
            font-size: 14px;
            margin-top: 15px;
            color: #555;
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        .final-score-container {
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            text-align: center;
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        .final-score-container h2 {
            margin-top: 0;
            margin-bottom: 30px;
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        .score-summary {
            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 40px;
            flex-wrap: wrap;
        }
        .score-card {
            background-color: #f8f9fa;
            border-radius: 12px;
            padding: 20px;
            width: 180px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.05);
            border: 1px solid #e9ecef;
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        .score-card h3 {
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            font-size: 16px;
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            font-size: 16px;
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        .score-details td:last-child {
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        .report-actions button {
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            font-size: 15px;
            line-height: 1.6;
            display: none; /* 默认隐藏 */
        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>WebSocket 与 HTTP 的区别 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，HTTP 和 WebSocket 最核心的区别在于它们的通信模式是什么？",
    "options": [
      "HTTP 是有状态的，而 WebSocket 是无状态的。",
      "HTTP 采用请求-响应的单向通信模式，而 WebSocket 采用全双工的双向通信模式。",
      "HTTP 只能传输文本数据，而 WebSocket 可以传输二进制数据。",
      "HTTP 是短连接，而 WebSocket 也是短连接，但效率更高。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档的核心差异表格明确指出，HTTP 的通信模式是“请求-响应，单向”，即通信必须由客户端发起。而 WebSocket 则是“全双工，双向”，连接建立后，客户端和服务器都可以随时主动向对方发送数据，这是两者最根本的区别。",
    "source": "文档中「基础概念对比」部分的「核心差异」表格",
    "hint": "回想一下文档中对比表格的第一行，它直接描述了两种协议的通信模型差异。"
  },
  {
    "question": "WebSocket 连接是如何建立的？",
    "options": [
      "它完全独立于 HTTP，通过一个全新的 TCP 握手过程来建立。",
      "它依赖于一次初始的 HTTP 请求，客户端在该请求中通过特定的头部字段请求将协议升级到 WebSocket。",
      "它通过 UDP 协议进行快速握手，以降低延迟。",
      "它需要浏览器安装特定的插件才能与服务器建立连接。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "WebSocket 的连接建立过程非常独特，它“借用”了 HTTP 协议来完成初始握手。客户端会发送一个标准的 HTTP 请求，但其中包含了 `Upgrade: websocket` 和 `Connection: Upgrade` 这两个关键的头部字段，以此来通知服务器希望将连接从 HTTP 升级为 WebSocket。",
    "source": "文档中「握手与协议升级」部分的「1. 握手过程的概述」",
    "hint": "文档中提到，WebSocket 的连接建立从一个标准的 HTTP 请求开始..."
  },
  {
    "question": "在 WebSocket 握手成功后，服务器会返回哪个 HTTP 状态码来表示协议切换成功？",
    "options": [
      "200 OK",
      "101 Switching Protocols",
      "301 Moved Permanently",
      "204 No Content"
    ],
    "correctAnswerIndex": 1,
    "explanation": "当服务器同意将协议从 HTTP 升级到 WebSocket 时，它会返回一个状态码为 `101 Switching Protocols` 的 HTTP 响应。这个状态码明确地告诉客户端，服务器已经理解并接受了协议切换的请求，接下来的通信将遵循新的 WebSocket 协议。",
    "source": "文档中「握手与协议升级」部分的「服务器响应」",
    "hint": "在握手过程中，服务器的响应有一个非常特殊的、以数字 '1' 开头的状态码。"
  },
  {
    "question": "为什么说 WebSocket 在高频通信场景下比 HTTP 的数据传输效率更高？",
    "options": [
      "因为 WebSocket 默认使用数据压缩，而 HTTP 不支持。",
      "因为 WebSocket 运行在比 TCP 更快的传输层协议上。",
      "因为 WebSocket 握手后，后续数据以轻量的“帧”格式传输，头部开销极小；而 HTTP 每个请求都需携带完整的、冗余的头部信息。",
      "因为 WebSocket 连接是加密的，减少了数据校验的需要。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "HTTP 的主要性能瓶颈之一在于其头部的开销。每个 HTTP 请求（即使是长连接下的请求）都必须包含完整的头部信息（如 Host, User-Agent等），这在频繁的小数据包通信中会产生大量冗余数据。相比之下，WebSocket 在一次握手后，后续通信使用数据帧，其头部非常简洁（通常只有2-10字节），极大地降低了协议开销。",
    "source": "文档中「数据格式与传输」部分的「4. 性能对比」",
    "hint": "思考一下两种协议在连续发送小消息时，除了消息本身，还需要额外发送哪些信息？"
  },
  {
    "question": "以下哪个应用场景最适合使用 WebSocket 而不是传统的 HTTP？",
    "options": [
      "用户提交注册信息的表单页面。",
      "显示一篇新闻文章内容的静态页面。",
      "需要实时显示股票价格变化的金融行情应用。",
      "用户下载一个PDF文件的服务。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "金融行情应用需要服务器能够实时、低延迟地将价格变动推送到客户端，而不需要客户端频繁地发起请求。这正是 WebSocket 的全双工和服务器推送能力的完美应用场景。其他选项如表单提交、静态内容加载和文件下载都是典型的“一次请求-一次响应”模式，非常适合使用 HTTP。",
    "source": "文档中「应用场景」部分的「1.2 实时推送」",
    "hint": "哪个场景最需要服务器主动、持续地向客户端发送数据？"
  },
  {
    "question": "根据文档，由于 WebSocket 采用长连接，它比 HTTP 更容易面临哪种特定的安全风险？",
    "options": [
      "跨站脚本攻击 (XSS)",
      "SQL注入攻击",
      "资源耗尽攻击（如攻击者创建大量连接耗尽服务器资源）",
      "密码暴力破解"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在安全性部分特别指出，WebSocket 的长连接特性使其面临“资源耗尽攻击”的风险。攻击者可以发起大量 WebSocket 连接并保持它们处于活动状态，从而消耗服务器的内存、CPU和网络连接数等资源，导致正常用户无法获得服务。而 HTTP 的短连接模式使得这种攻击的实现成本更高。",
    "source": "文档中「安全性」部分的「2.2 长连接中的安全风险」",
    "hint": "长连接意味着服务器需要为每个客户端“持续地”保留一份资源，如果这些客户端数量激增会发生什么？"
  },
  {
    "question": "在 WebSocket 通信中，数据传输的基本单位是什么？",
    "options": [
      "数据包 (Packet)",
      "帧 (Frame)",
      "消息体 (Body)",
      "请求 (Request)"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中明确说明，WebSocket 使用“帧（Frame）”作为最小的数据传输单元。与 HTTP 的完整请求/响应结构不同，WebSocket 将数据拆分成一个或多个帧进行传输。每个帧都有自己的头部，包含了操作码（Opcode）、数据长度等元信息，这种设计使其非常轻量和高效。",
    "source": "文档中「数据格式与传输」部分的「数据帧格式」",
    "hint": "文档中有一个描述 WebSocket 数据结构的图示，其标题就是答案。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
          }

          updateProgress();

          const currentQuestion = quizData[currentQuestionIndex];
          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
          currentQuestion.options.forEach((optionText, index) => {
            const li = document.createElement('li');
            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
                if (index === userAnswers[currentQuestionIndex]) {
                    li.classList.add('selected');
                }
            }
            optionsListEl.appendChild(li);
          });

          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
          }
          
          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
        }
        
        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  